JPS5847357Y2 - Safety device for double shell cryogenic tank - Google Patents

Description

[Detailed description of the invention] This invention is applicable to double-shelled low-temperature tanks for storing various low-temperature liquefied gases such as LPG and LNG.

This invention relates to a safety device for a double-shell low-temperature tank that is used in the event that stored liquid leaks from the inner tank or trouble occurs in the main valve for receiving and discharging.

As is well known, double-shell cryogenic tanks have a structure in which an inner tank is made of a metal with high low-temperature toughness, an outer tank is made of ordinary steel, and a heat insulating layer is provided between the inner and outer tanks. Things are common.

By the way, in a low temperature tank having this structure, the inner tank supports the stored liquid, and the outer tank mainly serves to maintain a heat insulating layer around the inner tank.

However, since the inner tank supporting the stored liquid is in direct contact with the low-temperature liquid, it is subject to repeated expansion and contraction due to changes in temperature as the stored liquid is taken in and out, changes in liquid load, and is exposed to an extremely harsh environment.

Therefore, although it is designed to be strong enough to withstand these environments, there is no guarantee that the stored liquid will never leak due to the conditions.

For example, there is a welding defect in the inner tank, which is amplified by expansion and contraction due to the addition and removal of the stored liquid, and as a result, the stored liquid leaks.

If the stored liquid leaks, it will naturally evaporate due to the outside temperature.

If that vaporization pressure is generated between the inner and outer tanks, in some cases,
This may cause damage to the outer tank, which in turn may lead to a major accident in which a large amount of stored liquid flows out of the tank.

Therefore, in order to prevent such dangers, it is generally required to install safety equipment such as installing a liquid barrier around the outer circumference of the tank or installing an emergency shutoff valve on the storage liquid receiving and discharging pipe. There is.

By the way, what about installing a liquid barrier around the tank?

It is necessary to secure a very large site depending on the capacity of the tank, which affects the construction cost and is also problematic from the point of view of effective use of the site.

Therefore, as a means to solve this problem, the outer tank itself is made of prestressed concrete that has sufficient strength and airtightness to withstand low-temperature liquids, so that even if the inner tank ruptures for some reason and the stored liquid leaks, A double-shell cryogenic tank has been proposed in which the water remains in the outer tank without further leaking out of the tank (see Figure 1).

By the way, when the outer tank 1 is made to function as a liquid barrier and the liquid receiving and discharging pipe 9 is connected in the conventional manner, that is, when it is installed outside the outer tank 1, which is the main valve for receiving and discharging, the main valve is As an emergency measure in the event of a breakdown, we have taken measures such as installing an emergency shutoff valve in parallel with the main valve to ensure safety.

However, if the outer tank is to function as a liquid barrier to ensure greater safety, it is preferable to provide the emergency shutoff valve or the like in the outer tank.

Therefore, this idea provides a double-shell cryogenic tank with high safety by installing safety devices such as a leak detection device and the above-mentioned emergency shutoff valve in the outer tank, and using the outer tank as a liquid barrier. It is.

In other words, a pit (Y) projecting outward is provided at the bottom of the outer tank of prestressed concrete structure, the storage liquid receiving and discharging pipe is passed through the pit na and connected to the inner tank, and an emergency shutoff valve is installed in the middle of the receiving and discharging pipe in the pit. In addition, the bottom of the pit is located below the bottom of the inner tank,
A communication chamber communicating with the gap between the inner and outer tanks is provided, and a leak detection device is provided within the communication chamber.

Hereinafter, a detailed description will be given based on examples.

1 is an outer tank of prestressed concrete structure; 3
is a pressure wall made of steel plates.

The lower part 2 of the outer tank 1 protrudes outward and is connected to the bottom concrete wall 4, and the pressure wall 3 hangs down and is fixed along the upper inner surface of the outer tank 1, and is fixed to the bottom concrete wall 4 at the lower end. A pit 5 is formed by a lower part of the outer tank 2, a pressure wall 3 and a bottom concrete wall 4.

The pit 5 has a bottom surface located below the bottom surface of the inner tank 10, has a manhole 6 at the top, and has an airtight lining 7 installed on the inner peripheral wall surface.

Next, 9 is a discharge pipe for the stored liquid, which passes through the pit 5 and is connected to the inner tank 10, and an emergency shutoff valve 11 is provided in the middle of the discharge pipe 9 inside the pit 5.

The passage of the discharge pipe 9 of the pit 5 is hermetically fixed as shown in the figure, and expansion joints 13 are provided at key points of the discharge pipe 9.

Furthermore, as shown in the drawing, an airtight communication chamber 15 is provided at the bottom of the pit 5, which communicates with the gap between the inner and outer tanks.

The communication chamber 15 includes a leakage detection device 16 or a leakage detection device 16 .

A safety device such as a ventilation pipe 16 for circulating inert gas or the like is connected.

In addition, in the figure, 8 is a ladder for going up and down in the pit, 12 is a pedestal for the emergency shutoff valve 11, and 14 is a main valve.

Since this invention has the above-described configuration, it has the following advantages.

First, the emergency shutoff valve of the liquid receiving and discharging pipe is located in the pit, i.e.
Since it is provided inside the prestressed outer tank, even if trouble occurs with the one-way valve, the stored liquid will be shut off within the outer tank by the emergency shutoff valve, and the stored liquid will not flow out of the tank.

Since the second emergency shutoff valve is housed within the pit, damage from wind and rain is reduced.

Thirdly, the communication chamber at the bottom of the pit can be equipped with safety devices such as a leak detection device or a ventilation pipe for circulating inert gas to discharge leaked liquefied gas, making it possible to install safety devices such as a leak detection device or a ventilation pipe for circulating inert gas to discharge leaked liquefied gas. Comparatively, safety is ensured.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of half of a double-shell cryogenic tank having an outer tank made of prestressed concrete, and FIG. 2 is an enlarged view of the main parts of the present invention. 1...Outer tank, 2...Lower part of the outer tank, 3...
...Pressure wall, 4...Bottom concrete wall,
5... pit, 6... manhole, 7
...Inner lining, 8...Ladder, 91. . ...Discharge pipe, 10...Inner tank, 11...
・Emergency shutoff valve. 12... Emergency shutoff valve pedestal, 13... Expansion joint, 14... Main valve, 15... Communication chamber, 16... Vent pipe or leak detection device.

Claims (1)

[Scope of utility model registration request] In a double-shell tank with an outer tank made of prestressed concrete, a pitna is provided at the bottom of the outer tank that protrudes outward, and a receiving and discharging pipe for the stored liquid is passed through the pit.
In addition to providing an emergency shutoff valve connected to the inner tank and in the middle of the receiving and discharging pipe in the pit, a communication chamber with a bottom surface located below the inner tank bottom plate and communicating with the gap between the inner and outer tanks is also provided inside the pit. A safety device for a double-shell low temperature tank characterized by having a leakage detection device installed in the communication chamber.